How to generate VIS output in CMAQ 5.3

CMAQ
#1

I want to get Visibility value. In CMAQ 5.2 I can set CTM_AVIS to ture to get VIS output. How to generate VIS output in CMAQ 5.3?

#2

Here are the VIS environment variable settings from a CMAQv5.2 run script:

setenv CTM_AVISDIAG Y        #> Aerovis diagnostic file [ default: N ]
  setenv CTM_VIS_1       "$OUTDIR/CCTM_PMVIS_${CTM_APPL}.nc -v"      #> On-Hour Visibility
  setenv CTM_AVIS_1      "$OUTDIR/CCTM_APMVIS_${CTM_APPL}.nc -v"     #> Hourly-Averaged Visibility

I don’t see that these are supported in the CMAQv5.3.2 code, but perhaps someone else knows.

#3

Please who has the solution to this, because neither WRF-CMAQ v.5.3.2/3 (coupled model) has visibility environment settings ?

#4

Earlier versions of CMAQ output visibility estimated near 550 nm using the below formula.

visibility = 10.0 log( (aerosol_extinction_550nm+Rayleigh_Extinction_550nm)/Rayleigh_Extinction_550nm)

The aerosol extinction was estimated two ways. One used a volume mixing model and an approximation of Mie Scattering Theory. The other used the IMPROVE reconstruction method. In current version of CMAQ, the In-line calculation of photolysis gives diagnostic outputs for the first estimate of aerosol extinction. In the PHOTDIAG3 file, the variable to used is EXT_AERO_W550 which has units of 1/km. For Rayleigh_Extinction_550nm, the visibility calculation should use 0.014 1/km. The number corresponds to what the In-line calculation computes for Rayleigh Scattering Extinction at 550nm.

Note that (aerosol_extinction_550nm+Rayleigh_Extinction_550nm) roughly corresponds to the total extinction. The PHOTDIAG3 file also contains the total extinction at several wavelengths but not at 550 nm. The value includes extinction from aerosols, ozone, nitrogen dioxide, Rayleigh Scattering and clouds. If the user wishes to use the PHOTDIAG3 values for total extinction, they have to interpolate EXT_W607 and EXT_W381 values for the total extinction at 550nm by using the Angstrom Exponents.

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#5

Forget to mention that Rayleigh_Extinction_550nm uses an air number density of 2.54E+19 molecules per cubic centimeter. For different number density, Rayleigh_Extinction_550nm equals approximately 4.499E-22 times the number density.